Field of the Disclosure
Embodiments of the present application relates to the art of a driving force control system for a hybrid vehicle having an engine and at least two motors for propelling the vehicle.
Discussion of the Related Art
JP-A-2011-063136 describes a driving device for hybrid vehicle. According to the teachings of JP-A-2011-063136, an operating mode of the hybrid vehicle can be selected from: electric vehicle mode in which the vehicle is powered by a motor while stopping an engine; series mode in which the vehicle is powered by the motor activated by an electric power generated by a generator driven by the engine; and series parallel mode in which the vehicle is powered by both of the engine and the motor. Specifically, the operating mode of the hybrid vehicle taught by JP-A-2011-063136 is shifted among the above-mentioned modes by manipulating two clutches and a brake. In addition, JP-A-2012-071699 describes a hybrid vehicle drive control device, and an operating mode of the hybrid vehicle taught by JP-A-2012-071699 may also be selected from the electric vehicle mode, the series mode, and the series parallel mode.
In the hybrid vehicles taught by JP-A-2011-063136 and JP-A-2012-071699, the operating mode is shifted depending on a vehicle speed and an opening degree of an accelerator. For example, in a case of shifting the operating mode of the hybrid vehicle taught by JP-A-2012-071699 from the electric vehicle mode to the hybrid mode such as the series mode or the series parallel mode, the brake is engaged first of all, and then the engine is started by the first motor. Thereafter, the brake is disengaged and the first clutch or the second clutch is engaged.
On the other hand, in a case of shifting the operating mode of the hybrid vehicle taught by JP-A-2012-071699 from the electric vehicle mode to the series parallel mode, the first clutch is disengaged first of all, and then the engine is started by the first motor while engaging the second clutch. Thereafter, the first clutch is engaged and the second clutch is disengaged.
Thus, according to the teachings of JP-A-2011-063136 and JP-A-2012-071699, when the operating mode is shifted to the mode in which the engine is started, the engine is started after manipulating any of the engagement devices, and then manipulating the clutches and the brake to establish the desired mode. However, as a result of engaging and disengaging those engagement elements frequently, engagement shocks may occur frequently.